In plastics manufacturing, the actual flow of polymer melts is transient, non-Newtonian and non-isothermal, with frozen layers building up as the complex mixture flows through the mold cavity. Characteristics of a finished product are determined by many complex factors, such as changes in the direction of flow, inclusion of ribs, and changes in thickness and holes. To control the quality of the products, a deep understanding of complicated flow fields is critical. Nowadays, CAE (computer-aided engineering) software provides realistic simulation and predictive analysis for complex flows of complex fluids.
According to results of academic research of fluid mechanics and rheology, a strain rate that indicates a rate of deformation of a material with respect to time plays an essential role in the physics of fluids. Strain contains shear and extension deformations. As a rule, both have been separately investigated.
In practice, a complex geometric channel flow is a combination of shear flow and extension flow. For the complex flow, a generalized strain rate that can be determined with certainty is widely applied in the CAE tool. Flows in injection molding are dominated by shear flows, but extension flows are encountered, such as the contraction flow at gate and nozzle regions, and the fountain flow of a melt front in the cavity. However, the generalized strain rate is not decomposed into individual rates of shear and extension. To resolve such significant issue, the present invention proposes the principal shear rate and principal extension rate to be obtained from the generalized strain rate. In addition, a new quantity is defined to show the degree of shear and extension variance with respect to flow geometric features. This is based on extensive research of complicated flow phenomena related to shear and extension.
This Discussion of the Background section is provided for background information only. The statements in this Discussion of the Background are not an admission that the subject matter disclosed in this section constitutes prior art to the present disclosure, and no part of this Discussion of the Background section may be used as an admission that any part of this application, including this Discussion of the Background section, constitutes prior art to the present disclosure.